Batch OS

Batch OS is a ancient(1950s) operating system used in mainframes like IBM 701 (1952), IBM 1401 (1959), etc.

In that period, the computer were less powerful in processing, memory (in every section in compare to today).

How Batch OS work:

1. The client give Jobs to the Operator (human).

2. The Operator groups same type of Jobs, Which is called Batch, and put it in the input device.

3. The Monitor programme (main os) executed the Job and gives output.

What is a Job?

Job = programme(.exe) + Data(input data) + control Instructions

In ancient period(1950s) computer could not do live interaction . Like, taking input data from user console. The client had to give the input data with the programme. Also, Job contained control instructions.

Control Instruction:

A simple Job Control Language(JCL)

$ JOB 001 // Start of a job

$ RUN payroll.exe // Run the program

$ INPUT employee_data.txt // Input source

$ OUTPUT salary_report.txt // Output destination

$ END // End of job

The control instruction instructed the OS where the starting point is, which programme to run, from where to read the input from, where to store the output and when to end.

Job storage devices: Jobs were stored Punched Card or in Magnetic Disk. Punched card were a cardboard with punched hole in it. In a cardboard the programme(e.g. Fortran) and other instructions were mapped into a pattern of punched hole and not holed area.

Batch: The client took jobs to The operator. Operator grouped same types of jobs like -

1. Programming language : COBOL, FORTRAN, ASSEMBLY.

2. Mathematical models

3. Printing Reports, Reading Tapes

The computation worked in First in First out method and single job at a time. Without batching if one jobs execution done then the resources like I/O devices, compiler, buffers, shared libraries of programming language get released. Then in the next job the computer needs to load necessary resources.

If we have 3 jobs. First and third jobs library and compiler are same. When the jobs executive without batching, the first one loads resources→executes programme→releases resources. The second and third one does the same. It is time consuming.

When the first and third jobs are batched, the first one loads necessary resources, after execution the os does not release the resources. The third job enters snd use the resources and executes. After all batched jobs execution the resources get released. Batch reduce redundancy.

Monitor: Monitor is the main programme or OS that executes the job. It controls cpu management, memory and resources management, i/o devices.

Than what is Batch OS?

Batch is the full system consisting

1. Monitor

2. Batching System

3. I/O Mechanisms

4. Scheduling (First in First out or Shortest job first logic)

Disadvantage of Batch: The Batch os did one job at a time. When a job needs i/o mechanisms the cpu sits idle as it takes time for i/o. No other job cold be executive in that time unlike multitasking os.

The control instruction on jobs tells the cpu where to store the output and ends the job execution. After that the batched jobs executes one after another.

After all batched job execution the resources get released and new resources for new batch are loaded and continue the cycle.